Project Summary The objective of this 3-year conference series is to develop and disseminate a research agenda for the study of implementation mechanisms to advance the ability of health systems to implement evidence based practices (EBPs) to improve the quality, safety, and efficiency of healthcare for Americans. Mechanisms can be defined as processes that are responsible for change. In the context of implementation science, mechanisms explain how or why implementation strategies exert their effects. The field of implementation faces its own knowing- doing gap, because researchers have failed to articulate and measure the causal pathway(s) by which strategies are hypothesized to effect change. Consequently, it is extremely difficult to replicate findings outside of a re- search program, learn from negative studies, or adapt an implementation strategy developed in one clinical setting to another. Moreover, without a fundamental understanding of implementation mechanisms, strategies cannot be tailored to the needs, resources, and barriers of a given context, which may have a disproportionate effect on settings in which priority populations receive their care as they are notoriously under-resourced. A focused, expert-led effort to recommend priorities, methods, and measures is needed to generate guidance and tools to test hypotheses related to strategy, mechanism, and outcome linkages, and whether they vary with respect to target problems, EBPs, priority populations, and context. This conference series is designed to achieve two aims. One, generate research, policy, and practice priorities for a research agenda to guide the study of implementation mechanisms. Two, actively disseminate the research agenda to research, policy, and practice audiences. A 26-member nationally-representative Mechanisms Network of Expertise (MNoE) will con- vene annually in a collaborative and structured ?Deep Dive? conference series. This conference series employs innovative methodologies to rapidly achieve this proposal's aims: concept mapping will reveal a research agenda and Implementation Development Workshops, along with manuscripts, webinars, brief reports, and short videos, will serve as vehicles for dissemination. Conference products will be informed by published literature, coding of recent conference presentations, policy and practice partner interviews, and expert opinion. The research agenda will serve as a guide for how to evaluate implementation mechanisms. In conducting mechanistic imple- mentation science, researchers will be able to ascertain how, why, and under what circumstances implementa- tion strategies work for whom and in what contexts to achieve more effective and sustained implementation. The results of the work made possible by the proposed conference series will directly inform policy maker and prac- tice leader decisions for improving healthcare through EBP implementation. Conference products will be dis- seminated via the nationally representative MNoE networks and internationally via listervs (e.g., Implementation Science News) social media (e.g., Twitter, ResearchGate), the Society for Implementation Research Collabora- tion website, and the VA Health Services Research & Development Cyberseminar series.